The present invention relates to a semiconductor diode and specifically to low leakage semiconductor diodes integrated with BCD technology.
In accordance with the known art a low leakage diode structure comprises a diffused anode region on which is provided a cathode region comprising a type N epitaxial layer with high resistivity and a type N highly doped region.
As known, the breakdown voltage of the junction of a low leakage diode depends on the characteristics of the epitaxial layer and in particular on the thickness of the epitaxial layer portion between the highly doped cathode region and the underlying diffused anode region.
More precisely, this value depends upon the distance between these two regions. The breakdown voltage depends also on the resistivity of the epitaxial layer. To increase this value without changing the manufacturing process (and incurring a resulting cost increase), it is necessary to act upon the thickness and/or resistivity of the epitaxial layer. However, these characteristics are generally fixed in such a manner as to optimize the performance of the power components which, with integrated circuits achieved with Bipolar/CMOS/DMOS(BCD) technology, are represented by DMOS transistors.
The technical problem underlying the present invention is to provide a semiconductor diode integrated with BCD technology having high breakdown voltage of the junction without changing the manufacturing process phases nor the characteristics of the epitaxial layer.
The disclosed inventions provide a diode structure in which the distance between the diffused anode region and the highly doped cathode region is increased without changing the diode manufacturing process nor the thickness and/or resistivity of the epitaxial layer.
The technical problem is solved by a semiconductor diode integrated with BCD technology, in which the anode is formed by a patterned updiffusion which is complementary to the patterned surface diffusion which provides the cathode contacts. (The cathode is formed by an epitaxial layer in combination with this surface diffusion.) The patterned updiffusion of the anode provides a junction contour with depressions in it, and these depressions are located opposite the surface diffusion portions of the cathode. Preferably this uses a process in which two buried layers are available, so that a lower buried layer can provide isolation.